lint-history example breaks with --filenames-important with a "delete file" commit

[thorbenk]

Thanks for this project!
I'm trying to use it to rewrite a repo to only use unix lineendings.
However, I'm running into an issue with lint-history together with --filenames-important (note: it does works when omitting --filenames-important).

Here is a minimal repo with which to reproduce this:

rm -rf /tmp/repo_with_delete
mkdir /tmp/repo_with_delete
cd /tmp/repo_with_delete

git init .
echo "A" > a.cpp
git add a.cpp
git commit -am "1"
git rm a.cpp
git commit -am "2"

export PYTHONPATH=/w/src/git-conversion/3rdparty/git-filter-repo/
/w/src/git-conversion/3rdparty/git-filter-repo/contrib/filter-repo-demos/lint-history --filenames-important dos2unix

I get:

dos2unix: converting file /tmp/tmp8vmqz50x/a.cpp to Unix format...
Traceback (most recent call last):
  File "/w/src/git-conversion/3rdparty/git-filter-repo/contrib/filter-repo-demos/lint-history", line 107, in <module>
    filter.run()
  File "/w/src/git-conversion/3rdparty/git-filter-repo/git_filter_repo.py", line 3813, in run
    self._parser.run(self._input, self._output)
  File "/w/src/git-conversion/3rdparty/git-filter-repo/git_filter_repo.py", line 1396, in run
    self._parse_commit()
  File "/w/src/git-conversion/3rdparty/git-filter-repo/git_filter_repo.py", line 1249, in _parse_commit
    self._commit_callback(commit, aux_info)
  File "/w/src/git-conversion/3rdparty/git-filter-repo/git_filter_repo.py", line 3363, in _tweak_commit
    self._commit_callback(commit, self.callback_metadata(aux_info))
  File "/w/src/git-conversion/3rdparty/git-filter-repo/contrib/filter-repo-demos/lint-history", line 64, in lint_with_real_filenames
    cat_file_process.stdin.write(change.blob_id + b'\n')
TypeError: unsupported operand type(s) for +: 'NoneType' and 'bytes'
fatal: stream ends early
fast-import: dumping crash report to .git/fast_import_crash_22223

I'm on commit 4ea19c0 of git-filter-repo.

[newren]

Thanks for the report! This commit that I just pushed fixes this:

commit 9d3d99593c88e0e0f6799c3bc83fa4a9c8f5cb01
Author: Elijah Newren <newren@gmail.com>
Date:   Thu Feb 6 13:00:48 2020 -0800

    lint-history: avoid dying when we get file deletions
    
    When a file is deleted, there is nothing to lint, so we can just keep
    the deletion as-is.
    
    Reported-by: Thorben Kröger <dev@thorben.net>
    Signed-off-by: Elijah Newren <newren@gmail.com>